Okay so my 1989 560SEL's cruise control has become possessed. It started about 4 months ago. At first it started not engaging at all. It just stopped working. Then it started working sporadically. Then is started working but setting its own speed. Then it started working fine for a few miles then shutting off. What the heck is going on with it??

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1973 280 - Sold
1980 300SD - Sold
1982 240D - Stolen
1988 300E - Sold
1989 260E - Sold
1989 560SEL
1994 E420 - Sold
1997 E420
2005 CL500